July 6, 2013 at 12:11 pm #84316
Recently I was flying our 414 we had purchased, with the former owner/instructor for familiarization training. On departure at approximately 150 feet on climb out the control yoke began a violent oscillation. The instructor took the control as he and I tried to determine what was causing the issue. The plane has an STec 60 AP. Within several seconds the oscillation stopped but the instructor encountered a strong downforce on the yoke. I assisted him holding the nose level as we returned to the field and successfully landed.
Upon exiting the plane we checked the tail and found the trim tab to be in the full nose down position. The cause was the bolt had fallen out of the connection on the actuator rod at the forward edge of the trim tab where it connects to the rod where it exits the horizontal stabilizer. That allowed the flutter which then caused the tab to over extend and the rod end jammed in the elevator causing it to stay in the full nose down position. This is when the oscillation of the yoke stopped and became a very heavy nose down pressure.
The owner had flown the plane for 6 years and approximately 600 hours. There had been no work involving the removal of that bolt during the time he owned the plane. How the cotter pin came out which allowed the bolt to come off is unknown. A new bolt, nut and cotter pin were installed and the plane is flying normally. The rigging of the trim tab was also checked. On preflight I am now lifting the elevator and visually inspecting that bolt/nut assembly and not just checking for play in the trim tab.July 6, 2013 at 8:48 pm #99460
A wise man (Jerry Temple) once told me, “if you do nothing else on your preflight, check the elevator trim tab actuator connector”. He said the failure can lead to an uncontrollable nose down condition.
I am glad you are okay!
Something we do not think about after incidents such as this is the NTSB reporting requirements.July 6, 2013 at 9:33 pm #99463rwelshParticipant
My guess would be a mechanic either replaced the bolt at the annual or some other time because of slop between the bolt and the clevis, and he/she never logged it. Of course the cotter pin was left out at that time. Cotter pins don’t wear out and then fall out of the hole even with the vibration in the elevator area.July 7, 2013 at 1:54 am #99467quote RWELSH:
I have seen cotter pins fail when they were the wrong size and not installed correctly, but this was a rotating component. I agree with you, it seems unusual in this case for it to be the cotter pin
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